Flow electrolytic column chromatography

As presently under discussion, the SISAK system coupled to a recoil separator [4] (see Sect 2.2.3. and Experimental Techniques ) may provide an alternative approach for continuously separating and detecting two oxidation states in Sg. The flow electrolytic column chromatography developed by Toyoshima et al. [117], which was successfully applied in on-line redox experiments of the heaviest actinides [118], may be adaptable to SISAK and may provide an interesting alternative approach for an electrochemical reduction of Sg. 

Recently flow coulometry, which uses a column electrode for rapid electrolysis, has become popular [21]. In this method, as shown in Fig. 5.34, the cell has a columnar working electrode that is filled with a carbon fiber or carbon powder and the solution of the supporting electrolyte flows through it. If an analyte is injected from the sample inlet, it enters the column and is quantitatively electrolyzed during its stay in the column. From the peak that appears in the current-time curve, the quantity of electricity is measured to determine the analyte. Because the electrolysis in the column electrode is complete in less than 1 s, this method is convenient for repeated measurements and is often used in coulometric detection in liquid chromatography and flow injection analyses. Besides its use in flow coulometry, the column electrode is very versatile. This versatility can be expanded even more by connecting two (or more) of the column electrodes in series or in parallel. The column electrodes are used in a variety of ways in non-aqueous solutions, as described in Chapter 9. 

Figure 26-7 Anion separation by ion chromatography with a gradient of electrolytically generated KOH and conductivity detection after suppression. Column Dionex lonPac AS11 diameter = 4 mm flow = 2.0 mL/min. Eluent 0.5 mM KOH for 2.5 min, 0.5 to 5.0 mM KOH from 2.5 to 6 min 5.0 to 38.2 mM KOH from 6 to 18 min. Peaks (1) quinate, (2) F, (3) acetate, (4) propanoate, (5) formate,...

Procedure (See Chromatography, Appendix IIA) Use a gas chromatograph equipped with an electrolytic conductivity detector operated in the halogen mode and fitted either with a capillary injector operated in the splitless mode or with a purged, packed injector with a glass insert. Use a 30-m x 0.53-mm (id), fused-silica column, or equivalent, coated with l-(xm Supelcowax 10 or an equivalent bonded carbowax column fitted with a 50-cm retention gap of 0.53-mm, deactivated, fused silica, or equivalent. Set the column temperature to 170° for 5 min, raise the temperature at a rate of 5°/min to 250°, and hold it at that temperature for 10 min. Maintain the injector temperature at 225°. Use helium as the carrier gas at a flow rate of 8 mL/min. 

ECL has also been used in detector cells in chromatography. These again involve the ECL of Ru(bpy)3, where detected species, such as amines, NADH, and amino acids, behave as the coreactant. In one method, post-column ECL detection, a solution of Ru(bpy)3" is steadily injected into the solution stream containing separated species coming from the HPLC column. The mixed stream flows into an electrolytic cell where the ECL reaction occurs and emission is measured (39). Detection of separated species at the picomole level is possible by this technique. Alternatively the Ru(bpy)3 can be immobilized in a film of Nafion on the working electrode (28), and the ECL signal results when the solution from the HPLC column contains a species that can act as a coreactant and produce emission by reaction with immobilized Ru(bpy)3 in the detector cell (40). Observation of ECL with flowing streams can also provide information about the hydrodynamics in the detector cell (41). 

Kirkland, and Ely (24) have discussed the SEC technique. Barth (25) has reported a practical approach to steric exclusion chromatography of water-soluble polymers. However, SEC is not easily carried out for the subject polymers because of the high molecular weight (10 -10 g/mole) and the poly-electrolyte characteristics of the charged polymers. In order to obtain meaningful SEC data, the columns, mobile phase, concentration of polymer solution, sample preparation method, flow rate, and shear degradation of the polymer should be considered in an SEC experiment. 

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